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QUESTION 9 Phosgene gas (COCI ) is formed by the following reaction. CO(g) + CL(g) = COCL(g) AH=-110 kJ mol! Which of the following statements is true for the system at equilibrium? (A) (B) (C) (D) Removing Cl (g) will increase the yield of phosgene and keep the K value constant. Adding a catalyst will increase the yield of phosgene and keep the K value constant. Increasing the pressure will increase the yield of phosgene and keep the K value constant. Decreasing the temperature will decrease the yield of phosgene and keep the K value constant
QUESTION 24 (5 marks) This table shows the effect of temperature on the pH of pure water. Temperature (ÔøΩC) Temperature CO a) Analyse the data to explain whether the self-ionisation of water is endothermic or exothermic. Explain your reasoning. [3 marks] b) Calculate the K of pure water at 50 ÔøΩC. Show your working. [2 marks] (to three significant figures)
QUESTION 25 (5 marks) This graph depicts the changes in concentration over time for a nitrogen dioxide / dinitrogen tetroxide gaseous equilibrium in a closed system at constant temperature. 0.120 0.100 fl = 0.080 + je) ÔøΩ & ÔøΩ 0.060 E 3 0.040 = fe) Y 0.020 0 20 40 60 80 100 120 140 160 180 200 220 Time (s) a) Determine the balanced chemical equation for the reaction in this system. [1 mark] b) Identify the time at which equilibrium is reached. [1 mark] c) Iftemperature is held constant predict the effect that doubling the volume at 100 seconds would have on the closed system by sketching the change that would occur and the approximate position of the new equilibrium on the graph. [3 marks] Note: If you make a mistake draw a line through this graph and use the additional graph provided on page 13 of this question and response book
QUESTION 2 (12 marks) Salicylic acid reacts with ethanoic anhydride in an aqueous solution to produce acetylsalicylic acid as shown in the equation. Acetylsalicylic acid is commonly known as aspirin. a) b) Cc) d) e) O On i O C CH /&ÔøΩ CH 3 7 ÔøΩ + CÔøΩOH As = CH-CÔøΩOH I ee: CÔøΩOH 3 O salicylic acid ethanoic anhydride acetylsalicylic acid ethanoic acid (C H 05) (C H 03) (C H O0 ) (C H 0 ) Identify the type of chemical reaction used to produce aspirin. [1 mark] Write the equilibrium expression K for the reaction. [1 mark] At 20 ÔøΩC the equilibrium constant (K ) for the reaction is 2 x 10ÔøΩ. Determine whether the concentration of the reactants or products is greater at equilibrium at this temperature. [2 marks] Calculate the minimum mass of salicylic acid required to produce 500.0 mg of aspirin if the yield of aspirin 1s 45.0%. Show your working. [4 marks] mg (to three significant figures) When the reaction is heated to 40 ÔøΩC and equilibrium is re-established the concentration of acetylsalicylic acid and ethanoic acid increases. Apply Le ChatelierÔøΩs principle to predict if the forward reaction is exothermic or endothermic. Explain your reasoning. [4 marks]
QUESTION 5 (17 marks) Compound A reacts with water to produce compound B and hydroxide ions. a) b) c) d) e) CH CH NH (aq) +H O(l) f C HsNH{ (aq) + OH (aq) A B Apply IUPAC rules to name compound A. Identify the Brensted-Lowry acids in the equation. A small amount of hydrochloric acid is added to the equilibrium mixture. Predict the effect of this on the concentration of compound A in the mixture. Explain your reasoning. Calculate the pH of a 2.0 M solution of compound A. State any assumptions. Show your working. (K =5.6x10-*) (to one decimal place) Describe using a balanced chemical equation how Compound A could be made from bromomethane. Include relevant conditions and reagents in your response. [1 mark] [2 marks] [3 marks] [6 marks] [5 marks]
QUESTION 10 Determine which system at equilibrium will shift to the right (products) if the total pressure on the system is increased. (A) N O0 (g) = 2NO (g) (B) 2H O0(g) = 2H(g) + O2(g) (C) 2S02(g) + O(g) = 2803(g) (D) CO(g)+H O(g) = CO (g) + Hp(g)
QUESTION 25 (5 marks) An equilibrium is formed between two differently coloured cobalt species Co(H 0) 2 * (aq) which is pink and CoCÔøΩ ~(aq) which is blue. The equation for this equilibrium is shown. a) b) Co(H 0) * (aq) + 4CI (aq) = CoC ÔøΩ (aq) + 6H 0(1) Apply Le ChatelierÔøΩs principle to predict the visible epee of adding AgNO; to an aqueous blue-coloured solution containing Co(H 0) 7* and CoClyÔøΩ ions. Explain your reasoning. When a sample of the equilibrium mixture is put into hot water the mixture turns more blue. Determine whether the forward reaction of the equation is exothermic or endothermic. Explain your reasoning. [3 marks] [2 marks]
QUESTION 4 (9 marks) 5.00 x 1074 moles of hydrogen gas 1s mixed with 1.00 x 10> moles of iodine vapour in a sealed 1.00 L vessel at 455.0 ÔøΩC. The concentration of hydrogen iodide gas formed at equilibrium is 9.30 x 104+ M. The balanced equation for the reaction is shown. H (g)+ L(g) = 2HI(g) a) Write the equilibrium law expression for the reaction. [1 mark] b) Calculate the equilibrium constant (K ) for the reaction at 455.0 ÔøΩC. Show your working. [5 marks] (to three significant figures) c) Predict the effect that adding a catalyst would have on the reaction rates position of the equilibrium and value of K . [3 marks]
QUESTION 6 The equilibrium concentration of A is 2.8 x 10* Mand Bis 1.2 x 107 M. A(g)=B(g) AH >0 Which option represents the ratio of molecules present in a sample of the gaseous mixture when the temperature is decreased and a new equilibrium established? (A) 8 molecules of A and 2 molecules of B (B) 5 molecules of A and 5 molecules of B (C) 3 molecules of A and 7 molecules of B (D) 2 molecules of A and 8 molecules of B
QUESTION 8 Predict how the system shown will respond when a small amount of aqueous sodium hydroxide is added. (A) (B) (C) (D) CH;COOH(aq) + H O0(1) = CH;COOÔøΩ (aq) + H30* (aq) Equilibrium shifts to the left and the pH decreases. Equilibrium shifts to the right and the pH increases. Equilibrium shifts to the left and the pH remains the same. Equilibrium shifts to the right and the pH remains the same
QUESTION 2 (8 marks) The reaction shows part of the contact process used to produce sulfuric acid. 280; (g) +O; = 280; (g) The equilibrium constant (X ) for this reaction at different temperatures is shown. Temperature (K) | Equilibrium constant K (mol L) 298 9.77 x 107ÔøΩ 500 8.61 x 10!! a) Deduce if the forward reaction is exothermic or endothermic. Explain your reasoning. [2 marks] b) Calculate the equilibrium concentration of SO; at 500 K given the equilibrium concentrations. [SO ] = 0.860 M; [O ] = 0.330 M [2 marks] Concentration = M (to three significant figures) c) Apply Le ChatelierÔøΩs principle to explain whether halving the reaction vesselÔøΩs volume at 500 K would affect the position of the equilibrium or the value of the equilibrium constant. [4 marks]
QUESTION 21 (4 marks) CO(g) reacts with O (g) in a sealed container producing CO (g) to reach equilibrium. 2CO(g) + On(g) == 2CO2(g) Apply collision theory to explain how increasing the concentration of O at equilibrium will affect the concentration of CO if the temperature and volume are held constant.
QUESTION 4 Identify which change would shift the system from light purple to dark purple. 2HI(g) = Hg) + L(g) AH = +53.6kJ mol! Colourless Colourless Purple (A) adding HI(g) (B) adding a catalyst (C) decreasing the temperature (D) increasing the concentration of H (g)
QUESTION 8 (7 marks) Two experiments were conducted to investigate the effect of temperature on the equilibrium formed during the decomposition of hydrogen iodide (HI). 2HI(g) = H (g) + L(g) AH = +53.6kJ mol! a POD Coma On Equilibrium concentration a L 1) (mol L) K cm fn [er fm Tt [| Experiment P80 fom 900 [om fa [a0 Fons [06 [ae [oa aoe (a) Determine the concentration of HI(g) and I (g) at equilibrium for experiment 1. [2 marks] [HI]: [In]: (b) Calculate the equilibrium constant (K ) for experiment 2. Show your working. [2 marks] (c) Determine which experiment was conducted at a higher temperature. Explain your reasoning. [3 marks]
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